Tigers right-hander Doug Fister has been on the disabled list since suffering a costochondral (rib cage) strain in the fourth inning of his April 7 start against the Red Sox. He was only supposed to be sidelined for the required 15 days, but it sure sounds like his absence will last longer than that.

According to Tom Gage of the Detroit News, Fister cut short a bullpen session after just 12 pitches Tuesday upon feeling pain in his abdominal region.

The Tigers aren’t calling it a setback, but they’re resigned to the fact that Fister is going to need more time.

“We’re backing off him for a couple of days to give him a chance to regroup,” said trainer Kevin Rand. “He stopped (throwing) because he was having some pain in his abdomen. At this point, we’re just being overly cautious because he wasn’t ready to let it go full-tilt.”

Fister, 28, registered a sparkling 2.83 ERA, 1.06 WHIP and 146/37 K/BB ratio across 216 1/3 innings last season between the Mariners and Tigers. Adam Wilk will continue to fill in for Detroit.